JP3002727B1 - Variable speed TDM switching system using TS connection - Google Patents

Variable speed TDM switching system using TS connection

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Publication number
JP3002727B1
JP3002727B1 JP21737998A JP21737998A JP3002727B1 JP 3002727 B1 JP3002727 B1 JP 3002727B1 JP 21737998 A JP21737998 A JP 21737998A JP 21737998 A JP21737998 A JP 21737998A JP 3002727 B1 JP3002727 B1 JP 3002727B1
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JP
Japan
Prior art keywords
time
switch
switching
division
tdm
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
JP21737998A
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Japanese (ja)
Other versions
JP2000050374A (en
Inventor
ウドムキャット ブンワォラセト
忠夫 斎藤
宗一郎 日高
仁 相田
輝勝 青木
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東京大学長
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Priority to JP21737998A priority Critical patent/JP3002727B1/en
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Publication of JP3002727B1 publication Critical patent/JP3002727B1/en
Publication of JP2000050374A publication Critical patent/JP2000050374A/en
Expired - Lifetime legal-status Critical Current

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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00Data switching networks
    • H04L12/54Store-and-forward switching systems
    • H04L12/56Packet switching systems
    • H04L12/5601Transfer mode dependent, e.g. ATM
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L49/00Packet switching elements
    • H04L49/10Switching fabric construction
    • H04L49/104ATM switching fabrics
    • H04L49/105ATM switching elements
    • H04L49/106ATM switching elements using space switching, e.g. crossbar or matrix
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00Data switching networks
    • H04L12/54Store-and-forward switching systems
    • H04L12/56Packet switching systems
    • H04L12/5601Transfer mode dependent, e.g. ATM
    • H04L2012/5638Services, e.g. multimedia, GOS, QOS
    • H04L2012/5646Cell characteristics, e.g. loss, delay, jitter, sequence integrity
    • H04L2012/5652Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00Data switching networks
    • H04L12/54Store-and-forward switching systems
    • H04L12/56Packet switching systems
    • H04L12/5601Transfer mode dependent, e.g. ATM
    • H04L2012/5672Multiplexing, e.g. coding, scrambling
    • H04L2012/5675Timeslot assignment, e.g. TDMA
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00Data switching networks
    • H04L12/54Store-and-forward switching systems
    • H04L12/56Packet switching systems
    • H04L12/5601Transfer mode dependent, e.g. ATM
    • H04L2012/5678Traffic aspects, e.g. arbitration, load balancing, smoothing, buffer management
    • H04L2012/5679Arbitration or scheduling

Abstract

Kind Code: A1 A variable rate TDM switching system suitable for handling video traffic is provided. A scheduler determines a time switching schedule for changing the order of time slots in the time division time switch based on contents of an input TDM frame header so that time slots of the same destination are time-dispersed. Then, a spatial switching schedule for opening and closing the time division gate in the time division space switch is determined so that only one time slot having the same outgoing line as a destination exists at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital switching system, and more particularly to a variable speed TDM switching system for processing variable speed traffic such as video traffic.

[0002]

2. Description of the Related Art As a conventional digital switching system, T
The DM method is widely used. The S switch (space switch), which is a TDM type switch, arranges time-division gates between incoming and outgoing lines, and opens and closes the time-division gates at a high speed, so that multiplexing is performed in units of time slots while being multiplexed. This is a switch that exchanges between outgoing lines. FIG.
It is a diagram explaining the principle of a switch. The S-switch is composed of a time-division gate and a control memory for controlling the opening and closing of the gate.
The process moves to the time slot on the outgoing line corresponding to the desired destination through the time division gate specified in the control memory. At this time, the time position of the time slot is preserved, and the time position of the incoming / outgoing line becomes the same. The control memory is prepared for each outgoing line, and stores which incoming line gate is opened and information is passed through for each time slot.

A T switch (time switch) is a switch for replacing a time slot on an incoming line with an arbitrary time slot on an outgoing line. FIG. 2 is a diagram illustrating the principle of the T switch. The T switch is used for the call memory (SP
M), a write control memory (SCM), and a sequential address counter, and when writing the information of the incoming time slot into the call memory, specifies the address of the call memory corresponding to the desired outgoing time slot. By sequentially reading the written information, the time positions of the time slots are exchanged. FIG. 2 shows an example of the configuration of the T switch for controlling the random write / sequential read. On the contrary, the T switch for controlling the sequential write / random read is used.
Switches are also feasible.

[0004] The TDM exchange has an advantage that once connection setup is completed, delay guarantee and loss rate guarantee can be reliably performed without performing special control such as flow control and congestion control. Currently, it is mainly used for voice communication with severe delay conditions.

[0005]

However, the TDM exchange has the following problems. The first problem is that the TDM exchange is originally a means for efficiently switching traffic of the same speed.
Switches do not operate efficiently, that is, it is difficult to handle multi-rate traffic.

The second problem is that in order to handle variable speed in the current TDM network, it is necessary to request a time slot at the maximum speed of the traffic, and the transmission efficiency becomes very poor. It is difficult to handle speed traffic efficiently.

[0007] Traffic with severe delay conditions includes video traffic in addition to the voice traffic described above.
MPEG2 is a typical moving picture encoding method, but encoding with this method usually generates variable-rate traffic. FIG. 3 shows an example of the MPEG2 stream. Assuming that the average use bandwidth of this traffic is about 1 Mbps and the maximum use bandwidth is about 5 Mbps, when using the conventional TDM switching method, the connection must be set at about 5 Mbps, which is the maximum use bandwidth. However,
Since the average use bandwidth of this traffic is about 1 Mbps, a transmission bandwidth of about 4 Mbps is wasted. Therefore, when attempting to handle moving image traffic using a TDM switch, it is important to solve the second problem, among the two problems of the existing TDM switching system.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional TDM switching system and to provide a variable speed T suitable for handling traffic with strict delay conditions, especially moving picture traffic.
The purpose is to provide a DM switching system.

[0009]

Accordingly, one embodiment of the variable rate TDM switching system according to the present invention is to place a time division gate at each of the intersections of a plurality of incoming lines and a plurality of outgoing lines,
By opening and closing these time-division gates at a high speed, input TDM is provided in front of each input line of the time-division space switch for exchanging input and output lines in time slot units while multiplexing.
A time-division time switch having a function of changing the order of time slots in a frame is connected, a scheduler for centrally controlling the time-division gate and the time-division switch is connected to the time-division gate and the time-division switch, and when a TDM frame header is input, a TDM frame is input. Is transferred to the scheduler, and based on the content of the header, the scheduler distributes the time switching schedule for the reordering of the time slots in the time division time switch so that the time slots of the same destination are temporally distributed. And determining the spatial switching schedule for opening and closing the time-division gates in the time-division space switch so that there is only one destination time slot at the same time and the same outgoing line. The switch is the temporal switch It said according to the schedule from TDM
A frame is temporally switched and input to the time division space switch, and the time division space switch switches each time slot to an outgoing line of each destination according to the spatial switching schedule.

Another embodiment of the variable speed TDM switching system according to the present invention is to arrange a time division gate at each of intersections of a plurality of incoming lines and a plurality of outgoing lines and open and close these time division gates at high speed. Thus, a time division time switch having a function of changing the order of time slots in an input TDM frame is connected to a stage preceding each input line of a time division space switch which performs switching between input and output lines in units of time slots while multiplexing. The time division gate and the time division time switch are connected to a scheduler for centrally controlling them, and a content analyzer for notifying the scheduler of information from a TDM frame header is connected. The header is forwarded to the content analyzer, and the content analyzer The TDM from the contents of the Muhedda
The scheduler notifies the scheduler of information about each time slot in the frame, and based on the information, the scheduler sets a time switching schedule for the time slot order change in the time division time switch to the same destination time. The slots are determined so as to be dispersed in time, and the spatial switching schedule for opening and closing the time-division gates in the time-division space switch is determined such that there is only one time slot to which the same outgoing line is addressed at the same time. And the time division time switch temporally switches the TDM frame according to the time switching schedule and inputs the TDM frame to the time division space switch.
According to the spatial switching schedule, each time slot is switched to an outgoing line of each destination. In this way, in the case of handling variable speed traffic, for example, if the connection setting is set to the average use band, if the data to be transmitted to a certain input is smaller than this average use band, this transmission band is Efficiently handle variable-rate traffic, because inputs can be used and if the data to be transmitted by one input is larger than this average bandwidth, then the other input can be borrowed and transmitted using available transmission bandwidth Can be. Conventional ATM
In the scheme, ATM cells are switched, but in the scheme according to the present invention, TDM frames are switched. For this reason, at a low load, the switching delay becomes larger than that of the ATM exchange. However, when the load is high, the buffering delay is large in the ATM exchange, whereas in the present invention, the time slots of the same destination are time-distributed by the time division time switch and input to the time division space switch. The space switch does not require a buffer, and the delay characteristics are greatly improved. In addition, conventional ATM
In the case of the system, since a header is added to each input ATM cell, a high-speed header processing is required in each exchange. In the method according to the present invention, since the header information of each time slot is all added to the head of the TDM frame, there is also an advantage that the header processing becomes easier as compared with the ATM exchange.

In the method of the present invention, since the time division space switch is bufferless, the scheduler must determine the spatial switching schedule so that only one time slot of the same destination exists at the same time. For example, the following two are conceivable as specific scheduling methods.

The first method is RSA (Rotation Selecti).
on Algorithm). FIG. 4 is a diagram for explaining the concept of the RSA scheme. FIG. 4 is a conceptual diagram when the number of inputs / outputs is 4 × 4 in the system of the present invention. Each row shows an input port number, and each column shows an output port number (destination).
The RSA method is a method of exchanging time slots in the order shown in FIG. That is, first of all, FIG.
a, a time slot from the incoming line 1 to the outgoing line 1, a time slot from the incoming line 2 to the outgoing line 2. . . And pack it at the beginning of the TDM frame. Subsequently, as shown in FIG. 4b, a time slot from input line 1 to output line 2 and a time slot from input line 2 to output line 3. . . Is selected and packed in the second of each TDM frame. Hereinafter, if time slots are packed by the same operation, only one time slot having the same destination can be used at the same time.

The second method is a GLQA (Global Longest
Queue Algorithm). FIGS. 5 and 6 show the GL
FIG. 3 is a diagram for explaining the concept of the QA method. The scheduler first sets the destination of each input time slot to T
The traffic matrix shown in FIG. 5 is generated from the DM frame header. However, the ij component of this matrix represents “the number of time slots from the incoming line i to the outgoing line (destination) j”. In the GLQA method, the largest number is first searched out from the traffic matrix. Then, find the maximum number excluding the row and column containing the maximum number. Hereinafter, four components of the traffic matrix are selected by the same operation (FIG. 6), but these time slots are packed at the head of each TDM frame. The same operation is repeated thereafter to select the second time slot and the third time slot of each TDM frame, so that only one time slot of the same destination is set at the same time. it can.

Still another embodiment of the variable rate TDM switching system according to the present invention is such that the spatial switching schedule is such that a different time slot of the incoming line is sequentially assigned to each TDM frame of the outgoing line. It is characterized in that it is determined.

In another embodiment of the variable rate TDM switching system according to the present invention, the spatial switching schedule is determined by counting the number of time slots used for each of the outgoing and incoming line pairs and selecting the time slot in descending order. It is characterized by doing.

FIG. 7 shows an example of the format of a TDM frame used in the variable rate digital switching system according to the present invention. Usually, the time slot length of a TDM frame is 1
The octet and the TDM frame period are about 125 μs. However, when handling moving picture traffic, it is more efficient to use a larger time slot length.
Large capacity becomes easy. In particular, in many video signal encoding schemes such as MPEG2, the frame period is 33 ms. Therefore, for example, the time slot length is 16 kbit, the frame period is 3.3 ms (transmission speed 622.08 Mbps).
), It becomes a divisor of the frame period used in these encoding methods, and it becomes possible to associate the video frame with the TDM frame. By this association, control for optimizing the moving image quality can be performed in the exchange, and the conventional exchange method (TD
Compared with the M switching system, the ATM switching system, the packet switching system, etc.), there is an advantage that the moving image quality can be improved even if the network quality is the same.

According to still another embodiment of the present invention, the time slot length of the TDM frame is 16 kilobits, and the frame period is a divisor of the image frame period of the input image signal.

[0018]

FIG. 8 shows a variable speed data according to the present invention.
FIG. 4 is a diagram illustrating the principle of an embodiment of a digital exchange system.
is there. The switch 1 according to the method of the present invention has a time-division time switch.
Itch 21, 2Two,. . . , 2iAnd scheduler 3
, Content analyzer 4 and time-division space switch 5
And a time division gate 6 provided in the time division space switch.
1,1, 6 1,2,. . . , 6i, jAnd the output buffer 71,
7Two,. . . , 7jAnd Time division time switch 2
1, 2Two,. . . , 2iIs similar to a conventional T-switch
Change the order of time slots in the input TDM frame
Function to change the time slot,
To follow the instructions of Jura 3
Intermittent switching itself is not the purpose,
For the purpose of distributing the traffic input to the split space switch 5
Is different from the conventional one. Time division space
The switch 5 has an input TDM switch similar to the conventional S switch.
It has the function of spatially switching frames,
Wari gate 61,1, 61,2,. . . , 6 i, jEach opening and closing
Is different from the conventional one in that scheduler 3 controls
ing.

Referring now to FIG. 8, the operation of the variable rate digital switching system according to the present invention will be described as an example. FIG.
In the case of transmitting a TDM frame as shown in (1), the content analyzer 4 reads the header of the TDM frame and
Information such as the destination and priority of each time slot in the M frame is transferred to the scheduler 3. The scheduler 3 derives the time division time switch 2 1 ,
2 2 ,. . . , 2i determine how to perform time slot switching (temporal switching),
The scheduling information is transmitted to the time division time switch 2 1 ,
2 2 ,. . . , To notify the 2 i. Time division time switch 2
1 , 2 2 ,. . . , 2 i actually execute temporal switching (time slot replacement) based on the scheduling information from the scheduler 3. This temporal switching has a function of temporally distributing time slots input to the time division space switch 5.

The time division time switches 2 1 , 2 2 ,. . . ,
The TDM frame temporally switched in 2 i continues to be input to the time division space switch 5. Since the time division space switch 5 is bufferless, it is necessary that only one time slot of the same destination exists at the same time. For this reason, the scheduler 3 performs spatial switching scheduling for opening and closing each time division gate in the time division space switch. As an actual scheduling method for performing this scheduling, there are, for example, the RSA method and the GLQA method as described above. By opening and closing each time-division gate based on this scheduling information, each time slot is assigned to the output buffer 7 1 , 7 2 ,. . . , 7j .

In the above embodiment, the content analyzer examines the frame header, and the scheduler performs scheduling based on the information. However, the content analyzer is omitted, and the scheduler performs scheduling directly from the contents of the frame header. It is also possible to configure.

[0022]

According to the present invention, there is provided a variable-speed TDM switching system suitable for handling traffic with strict delay conditions, particularly moving image traffic.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of a conventional S switch.

FIGS. 2A and 2B are diagrams illustrating the principle of a conventional T-switch. FIG.

FIG. 3 is a graph showing an example of an MPEG2 stream.

FIG. 4 is a diagram for explaining the concept of the RSA scheme.

FIG. 5 is a diagram for explaining the concept of the GLQA scheme.

FIG. 6 is a diagram illustrating the concept of the GLQA scheme.

FIG. 7 is a diagram showing an example of the format of a TDM frame used in the variable rate digital switching system according to the present invention.

FIG. 8 is a diagram illustrating the principle of an embodiment of a variable rate digital switching system according to the present invention.

[Explanation of symbols]

1 switch 2 1 to 2 i time division time switch 3 scheduler 4 content analyzer 5 time division space switch 6 1,1 to 6 i, j time division gate 7 1 to 7 j output buffer

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Bunwaraset Udomcat 1-5-7 Nishi-Ayase, Adachi-ku, Tokyo Lumiere Nishi-Ayase 605 (56) References JP-A-48-62314 (JP, A) JP-A-6-233337 (JP, A) JP-A-1-177799 (JP, A) JP-A-6-29970 (JP, A) JP-B-44-2423 (JP, B1) (58) Int.Cl. 7 , DB name) H04Q 11/00 H04L 12/28

Claims (5)

(57) [Claims]
1. A time division gate is arranged at each intersection of a plurality of incoming lines and a plurality of outgoing lines, and these time division gates are opened and closed at a high speed, so that the incoming and outgoing lines can be multiplexed in time slot units. A time division time switch having a function of changing the order of time slots in an input TDM frame is connected to a stage preceding each input line of the time division space switch for performing switching between the time division space switches, and these are connected to the time division gate and the time division time switch. When a TDM frame header is input, the header of the TDM frame is transferred to the scheduler, and the scheduler determines the order of the time slots in the time division time switch based on the contents of the header. The time switching schedule for the swap is divided into And determining the spatial switching schedule for opening and closing the time-division gates in the time-division space switch so that there is only one destination time slot at the same time and the same outgoing line. A switch temporally switches the TDM frame according to the temporal switching schedule and inputs the TDM frame to the time division space switch. The time division space switch outputs each time slot to each destination according to the spatial switching schedule. A variable speed TDM switching system characterized by switching to a line.
2. A time division gate is disposed at each intersection of a plurality of incoming lines and a plurality of outgoing lines, and these time division gates are opened and closed at a high speed, so that the incoming and outgoing lines can be multiplexed in time slot units. A time division time switch having a function of changing the order of time slots in an input TDM frame is connected to a stage preceding each input line of the time division space switch for performing switching between the time division space switches, and these are connected to the time division gate and the time division time switch. A scheduler for centrally controlling the TDM frame is connected to the scheduler, and a content analyzer for notifying the scheduler of information from the TDM frame header is connected. When the TDM frame header is input, the header of the TDM frame is transferred to the content analyzer. From the contents of this TDM frame header, The scheduler notifies the scheduler of information about the slot, and based on the information, the scheduler determines the time switching schedule for the rearrangement of the time slot order in the time-division time switch by the time slot of the same destination in time. The time-division switch is determined to be distributed, and the spatial switching schedule for opening and closing the time-division gates in the time-division space switch is determined so that only one time slot of the same outgoing line exists at the same time. A time switch temporally switches the TDM frame according to the temporal switching schedule and inputs the TDM frame to the time division space switch, and the time division space switch assigns each time slot to each destination according to the spatial switching schedule. Switch to outgoing line A variable speed TDM exchange method characterized by performing switching.
3. The variable speed TD according to claim 1, wherein:
A variable rate TDM switching system in the M switching system, wherein the spatial switching schedule is determined such that different TDM frames of the incoming line are sequentially allocated to each TDM frame of the outgoing line.
4. The variable speed TD according to claim 1,
In the M-switching system, the spatial switching schedule is determined by counting the number of time slots used for each of the outgoing and incoming lines and selecting the time slot in descending order.
5. The variable rate TDM switching system according to claim 1, wherein a time slot length of said TDM frame is 16 kilobits, and a frame period is a divisor of an image frame period of an input image signal. A variable speed TDM exchange system, characterized in that:
JP21737998A 1998-07-31 1998-07-31 Variable speed TDM switching system using TS connection Expired - Lifetime JP3002727B1 (en)

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JP21737998A JP3002727B1 (en) 1998-07-31 1998-07-31 Variable speed TDM switching system using TS connection
US09/363,649 US6628650B1 (en) 1998-07-31 1999-07-30 Variable rate TDM switching system

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